The present invention relates to a fuel injection controller for an internal-combustion engine. More particularly, the invention relates to a fuel injection controller capable of changing over the operating mode of the fuel injection system of a multicylinder internal combustion engine between a sequential fuel injection mode in which fuel is injected sequentially to the cylinders, and a simultaneous, group fuel injection mode in which fuel is injected simultaneously to the cylinders of each of two cylinder groups.
A known sequential fuel injection system for a multicylinder engine injects fuel in a sequential fuel injection mode. In this mode, fuel is injected in synchronism with TDC (top dead center) pulses. Each of these pulses indicate the top dead center corresponding to the start of an intake or suction stroke. The fuel is injected sequentially to the respective cylinders corresponding to the TDC pulses. A known simultaneous fuel injection system for a multicylinder engine injects fuel at a predetermined phase simultaneously into a plurality of cylinders while the engine is operating under high-load and high-speed operating conditions, where the fuel injection time interval is longer than the period of TDC pulses.
The known sequential fuel injection system delivers fuel efficiently to the cylinders, while the known simultaneous fuel injection system delivers fuel at a high rate sufficient for high-load and high-speed operation of the engine.
A simultaneous group fuel injection system for injecting fuel simultaneously into the cylinders of each of two cylinder groups is also known in the art. Japanese Patent Publication No. 47-38328 discloses a fuel injection controller which employs the simultaneous group fuel injection mode and sequential fuel injection mode selectively, depending on the operating condition of the engine to improve the performance of the engine.
However, problems arise in delivering fuel properly to the cylinders of the engine when the sequential fuel injection mode and the simultaneous group fuel injection mode are employed (selectively according to the operating condition of the engine) by directly changing the fuel injection mode from the sequential fuel injection mode to the simultaneous group fuel injection mode or vice versa.
One example is that the fuel injection mode is changed from the sequential fuel injection mode to the simultaneous group fuel injection mode immediately before a TDC pulse is generated for one of the cylinders at the start of the suction stroke. Since a time interval corresponding to one fuel injection cycle has elapsed from the preceding fuel injection for this cylinder, it is possible, depending on the timing of simultaneous group fuel injection, that no fuel is delivered to this cylinder for a time interval corresponding to two fuel injection cycles. To obviate such a possibility, the foregoing known fuel injection controller adds additional pulses to a fuel injection valve driving pulse signal. Alternatively, the pulse duration of the fuel injection valve driving pulse signal is extended to deliver a predetermined quantity of additional fuel in changing the fuel injection mode from the sequential fuel injection mode to the simultaneous group fuel injection mode.
However, such compensation measures require a special circuit for generating additional pulses or for increasing the pulse duration, which makes the configuration of the fuel injection controller complicated. Hence such known techniques are generally not practical.
The present invention also relates to an internal-combustion engine controller comprising fuel injection timing means and ignition timing means as components which function on the basis of signals representing the crank angles or instantaneous crank positions of an internal-combustion engine.
Generally, fuel injection timing and ignition timing of a multicylinder internal-combustion engine having a fuel injection device are controlled electrically by a controller. In the engine, a fuel injection angle for each cylinder corresponds to a suction or intake valve opening angle for the same cylinder. That is, in controlling fuel injection timing, the top dead center (TDC) of a suction stroke of each cylinder is detected and the fuel injection device is actuated at the TDC. On the other hand, an ignition angle is set to a crank angle before the TDC of a compression stroke. This crank angle must be set accurately according to the operating condition of the engine. Also, fuel injection timing must be controlled more accurately than ignition timing, because the advance ignition position and the retard ignition position relative to the TDC of a compression stroke has a direct effect on the performance of the engine.
Thus, in the engine, the start of fuel injection timing control and the start of ignition timing control are different from each other.
Accordingly, the conventional internal-combustion engine controller comprises TDC detecting means for generating a TDC pulse signal (hereinafter TDC signal) every time the piston of each cylinder arrives at a position corresponding to a crank angle before the TDC of the suction stroke by a predetermined angle (for example, in a six cylinder engine, every time the crankshaft turns through an angle of 120.degree.). Cylinder discriminating means are provided for generating a cylinder pulse signal CYL signal when a crank corresponding to a specified cylinder is at the TDC of a suction stroke, to carry out fuel injection cycles for the plurality of cylinders in a predetermined order by discriminating each cylinder corresponding to each TDC signal. Fuel injection timing operation is controlled on the basis of the output signals of the TDC detecting means and the cylinder discriminating means, namely, the TDC signal and the CYL signal. On the other hand, to enable accurate ignition timing control as mentioned above, another conventional internal-combustion engine controller comprises first pulse signal generating means for generating a pulse signal when the crank of each cylinder is at the TDC of a compression stroke, and second pulse signal generating means for generating a pulse signal every time the crankshaft turns through a predetermined angle (for example, 30.degree.) to divide the interval between the TDCs of the cylinders into equal angular intervals (a predetermined number of stages S). This conventional internal-combustion engine controller determines a fixed stage S in which ignition is started from the output signals of the two pulse signal generating means for accurate ignition timing control suitable for the operating condition of the engine.
To enable such accurate ignition timing control, Japanese Patent Application No. 60-31628 proposes an ignition timing controller comprising: projections arranged at regular angular intervals (for example, a crank angle of 30.degree.) on the circumference of a rotary member which rotates together with the crankshaft, excluding at least a portion of the circumference of the rotary member corresponding to the two equal angular intervals; first pulse signal generating means for generating a pulse signal every time each of the projections pass by a fixed position; and second pulse signal generating means for generating pulse signals having a predetermined phase difference relative to the output pulse signals of the first pulse signal generating means. This known ignition timing controller discriminates, on the basis of the output signals of the first and second pulse signal generating means, a cylinder corresponding to a crank at the TDC of a compression stroke and divides the angular interval between two TDCs into a plurality of stages S to achieve accurate ignition timing control on the basis of the stages S.
Recently, it has become desirable to make such an internal-combustion engine controller into a compact and simple configuration to reduce the manufacturing cost. However, the foregoing conventional controller needs at least four crank angle detecting means for fuel injection timing control and ignition timing control. Hence the conventional controller is unable to be made in a compact and simple configuration.